This card is like "Urth" But even better. You can untap This creature at the end of each turn. It gets blocker ability when you have no more shields left!

6Kuukai, Finder of Karma

This has more power than any other blocker in the light civilization. Not only that, but it untaps after every block, allowing it to fend off massive numbers of creatures all by itself! Not only that, but it's an evolution creature that only costs 5 mana!